I'm pretty sure that the information you want is in this thread:
http://www.yorkietalk.com/forums/sit...ions-talk.html from what I can recall, it's not cumulative, and a gift less than $20.00 does not have the words, "donating member", but just says donating and your status. You also don't get some of the other benefits, which include a larger avatar, posting in the "Yorkie Classified" Section, and being able to participate in the YorkieTalk gift exchange. So it might be better to save up until you get all the goodies.